Grinding machine



May 3, 1932. w. J. GUILD GRINDING MACHINE Filed May 9; 1928 5 Sheets-Sheet l g'wuml oo (Dalclo 3. Guild.

May 3, 1932. w. J. GUILD GRINDING MACHINE Filed May 9, 1928 5 Sheets-Sheet 2 Zlwwntw waldo 1 Guam May 3 1932..

W. J. GUILD GRINDING MACHINE Filed May 9, 1928 5 Sheets-Sheet 3 Waldo I Guild,

attorney y 1932- w. J. GUILD 1,856,185

GRINDING MACHINE Filed May 9, 1928 s Sheets-$heet 4 May 3, 1932.. w GLHLD 1,856,185

GRINDING MACHINE Filed May 9, 1928 5 Sheets-Sheet 5 F gjwuanhw Waldo I Guild,

Patented May 3, 1932 UNITED STATES PATENT OFFICE wanno a. GUILD, or woncasrnn, massacnnssr'rs, ASSIGNOR 'ro THE HEALD ma- CHINE OOMPANY, OF WORCESTER, MASSACHUSETTS, A

CHUSETTS CORPORATION OF MASSA- enmnme MACHINE The present invention relates to grinding machines, particularly of the internal type, and contemplates a machine which is adapted to grind a plurality of workpieces (or one workpiece having a plurality of surfaces to be ground) to predetermined sizes or dimensions, the grinding operation on each work-.

piece surface being, automatically terminated as soon as, but not before, the particular sur- 19 face being ground has arrived at the finished size.

The main object of the invention is to provide a grinding machine fulfilling the above conditions. Owing to the fact that grinding wheels do notv have an absolutely uniform consistency and, no matter how carefully graded, vary among themselves, it is impossible, in the ordinary grinding machine having no automatic means of control, to estab- 20 lish any accurate relationship between two or more grinding wheels and those mechanisms producing the cutting feed for such wheels, that will insure the completion of one surface being operated upon, simultaneously 3 with the completion of grinding on another given surface. With the use of a calipering mechanism and automatic instrumentali'ties to cause the grinding to cease whenone surface has reached a particular size, there would still be no assurance that such termination of the grinding would correspond with any predetermined size of any other surface be ing operated upon. If two separate caliperv ing mechanisms were employed each surface could be brought to accurate size in accordance with the separate mechanisms, but there would then be no relationship between the rates of grinding that could be relied upon, and the time element would be totally indeterminate. Such a machine would,indecd, consist in little more than two grinding mechanisms mounted upon a single base operating independently and would have all the disadvantages of such an arrangement. By utilizing, however, the grinding system or control which is the subject matter of my own prior invention and which is disclosed in a copending application Serial-1N0. 48,734 filed on August 7, 1925, now Patent No. 1,682,672, granted August 28, 1928, in which the cutting surface of a grinding wheel, by a dressing operation, is definitely made tangent to a known plane but slightly removed from the finished surface locus of a workpiece, and the grinding wheel is subse uently advanced through a. limited distance eyond said plane, I am enabled as hereinafter described. to synchronize a plurality of grinding operations so that they will be completed at the same instant. 6

In carrying out the present invention I cause a plurality of grinding wheels to move in unison in relation to the work surfaces which they are operating upon ;-that is to say when one grinding wheel is moving on that stroke of its relative traversing movement that carries it into the workpiece .every other grinding wheel is doing the same; and y when one grinding wheel is reversed in relation to its workpiece every other grinding wheel is so reversed whether or not the length of the traversing strokes be the same. Furthermore the cutting feet is actuated synchronously in respect to the grinding of the several work surfaces. This, therefore, is another object of the invention and in carrying it out I have shown an illustrative embodiment in which the work is held in a single rotating chuck and a pair of grinding wheels are given traversing motions in relation to this chuck which are opposite in direction.

It is a further object of the invention to provide means for the synchronization of the motion of the grinding tables, and this is accomplished by positive rack and gear connections, whereby the tables must always travel at least at a definite speed relationship and be reversed at the same time.

A further object of the invention is theretention ofijthe advantages of fluid pressure actuation of the tables together with the ositive mechanical connections already set orth and to that end the invention provides fluid pressure actuating means for each table with a single control mechanism which is governed by the motion of a-single table.

The above and other advantageous fea I t-ures of the invention will more fully appear 1 0 in the following detailed description, taken 0 in connection with the accompanying drawings, in which Fig. 1 is a front elevation of a grinding machine embodying the invention.

Fig. 2. is a rear elevation of the said machine.

Fig. 3 is a sectional view, on the line 3, 3 of Fig. 1, and showing the work head and lateral feeding mechanism.

Fig. 4 is a fragmentary elevational view of the rear of the machine, with certain parts removed, showing the cross slide ways and a certain fluid pressure, cylinder in section.

Fig. 5 is an' isometric view showing the actuating mechanism for the transverse feed detached from the machine.

Fig. 6 is a detached isometric view showing certain table controlling mechanism.

Fig. 7 is a detached isometric view of certain speed control and dresser actuating mechanism.

Fig. 8 is a fragmentary view of the table synchronizing mechanism, the tables or carriages being shown in section.

Fig. 9 is a diagrammatic or schematic view of the fluid pressure actuating mechanism for the machine.

Fig. 10 is a wiring diagram.

Like reference characters refer to like parts in the different figures.

Referring particularly to Figs. 1 and 2, the machine provides a pair of reciprocatory tables or carriages 1 and 2 of the same general type as the single table or carriage provided in the ordinary internal grinding machine. Said tables respectively carry wheel heads 3 and 4 of usual construction for the support of grinding wheels 5 and 6 mounted on rotatable spindles 7 and 8, the latter projecting in opposite directions for the operative engagement of said wheels with workpieces mounted in a rotatable chuck 9 that is open at both ends, and mounted in a centrally located workhead 10 betweenvsaid tables.

In' the machine herein illustrated the grinding wheels are rotated at high speed in any usual manner, for instance by belt drive, Figs. 1 and 2, from motors 11 and 12 carried by the tables 1 and2 respectively. The one or more I workpieces which may be mounted in the single chuck 9 are rotatedata slower speed,

' such rotation being imparted from a motor 13 mounted on the back of the machine base. As shown in Figs. 2 and 3, a belt 14 passes around the chuck 9 and through slots 15, 16 provided by the work head 10, said belt passing downwardly to a drivingpulley 17 located on a horizontal drive shaft 18 that is rotated by the motor 13. A spring actuated belt tensioning device 19 removes whatever sTack there may be in the belt and allows of limited motion of the work head lOtransverse to the direction of reciprocation of the tables 1 and 2, said transverse motion to feed the wheels and workpieces in cutting relation being hereinafter described.

So far as it relates to certain aspects of the present invention, the back and forth move ment of the tables 1 and 2 to cause the rotating grinding wheels 5 and 6 to make the required interior traverse of rotating workpieces may be imparted in any well known manner. Preferably, however, fluid. pressure controlling and reversing mechanism of the type disclosed in U. S. Letters Patent No. 1,582,468 to Heald and Guild is employed- According to the present invention, a single controlling and reversing mechanism is utilized, said mechanism being actuated from the movement of one of the tables (as herein shown the table 1) which providesspaced 23djustable dogs 20 and 21, adapted to alternately engage and move an interposed member 22, whose position controls the direction of travel of both tables. nected, as by connections shown in the afore: said Heald and Guild patent, to a rotatable Said member is convalve member 23. The valve member 23 may be of the form shown in the above mentioned patent, or it may be of the simplified construction illustrated in Fig. 9 of the present drawings; at all events when in one extreme position it admits fluid to the outside ends of a pa r of cylinders 25 and 26, which contain pistons, not shown, that are connected by piston rods 27 and 28 with the tables 1 and 2 respectively; while in the other extreme position of said valve member 23 fluid is admitted to the adjacent ends of said cylinders.

Referring now to the fluid pressure diagram of Fig. 9, the reversing valve member 23 is located in a suitable casing 29 on the front of the machine,'which casing provides a passage 30 to lead the pressure fluid to said valve, said casing also providing an exhaust passage 31, and passages 32 and 33 to lead the fluid to the different ends of said cylinders 25 and 26. Fluid is forced by a pump 34 into a supply pipe 35 which connects to the pa sage 30; the exhaust passage 31 is connected by means of piping 36 to the usual sump or tank located in the machine base, and not.

herein shown. The passage 30 is provided with a rotatable plug or throttle valve 37, the angular position of which can be adjusted from the front of the machine by means of a handle 38, in order to set the normal rate of speed of the tables 1 and 2.

The passage 32 connects, by means of piping 39 and 40., tothe right-hand end of the cylinder 25, and by means of piping 39 and 41, to the left-hand end of cylinder 26, the pipes 40 and 41 being branches of the pipe 39,

as clearly shown in the aforesaid fluid pres sure diagram. In similar fashion the pas-. sage 33 connects by means of piping 42 and branches 43 and 44 to the left-hand end of the cylinder 25 and the right-hand end ofthe cylinder 26. It is obvious, therefore, tha

when the valve 23 is in the position shown in Fig. 9 the pressure fluid will be admitted to sures that they will move oppositely'and be reversed at the same time, but, owing to the non-positive nature of the drive, and because there is nothing to compel equal quantities of fluid to enter each cylinder, there is no assurance that the tables will travel at the same speed, and consequently no assurance that they will be reversed when located at the same distance from the center of the work head 10. In fact, as the resistance against one table may be, and often is, different from that against the other table, due to difference in the friction of the several ways or other causes too numerous to'mention, the table 2, unless the further mechanism which will now be described were provided, might ultimately undergo its reciprocation in an entirely different position relative to the work head 10 from the table 1, the position of which alone is accurately controlled by the fluid pressure actuating mechanism, by reason ,of the fact that the controlling dogs 20 and 21 are attached to it. In order, therefore, to retain the advtantages of the fluid pressure method of table actuation, and the single control thereof, and yet keep the tables always in the same relative position on the opposite sides of the work head 10, the tables are connected together bv mechanical means, which will now be described. I

As shown in Fig. 8, each table 1 and 2 provides a rack, 47 and 48 respectively, attached to its under side. Meshing with one of these racks is a spur gear 49, rotatably mounted on a stationary stud 50, while a.

somewhat smaller spur gear 51, mounted on a stationary stud 52, meshes with the other rack. The gear 49 meshes directly with a,

long rack 53 that is supported on flanged rollers 54 and 55 which are rotatably mounted on stationary 'studs56 and 57. The gear 51 meshes with a gear 58, mounted on a stationary stud 59, and said;.-gear 58 meshes with the long rack 53. ,It will at once be seen that the tables 1 and 2 are connected positively and must move in opposite directions at equal rates of speed, from the fact that there .are two gears 51 and 58 interposed between one table rack and the long rack 53 and only one between the other table rack and said long rack. It is, of course, entirely im; material which table rack connects to the long rack through the single gear, and which through the two gears, except that the original positioning of the long rack in relation to the tables is dependent upon this selection.

The aforesaid stationary studs 50, 52, 5,4, 55 and 59 are conveniently fastened to the inside of the base of the machine,'said base comprising front and back walls 60 and 61 with a space between them, as is common in internal grinding machines. The positon of the spur gears 49, 51 and 58 and of the rack 53 in relation to the machine as a whole can be clearly seen in dotted lines inFig. 2.

The work head 10 is carried by a cross slide 10a which is mounted on ways 62 provided by the base of the machine, for the movement of said work head laterally in respect to the grinding wheels 5 and 6. Re-

ferring now to Fig. 3, a transverse feeding element for said cross slide, here shown as a screw shaft, is indicated by the numeral. 63. Rotation of this shaft in a clockwise direction (in this particular embodiment of the invention) is adapted to draw the work head to cause a workpiece or workpieces therein to move in cutting relation to the rinding wheels 5 and 6., Said screw sha t. 63 is adapted to be rotated manually by means of a hand wheel 64 and mechanically from a ratchet wheel 65, the latter being automatically given a step-by-step movement, as will hereinafter appear. Ratchet wheel 65 is directly fastened to an annular piece 64a,

which is herein shown as formed integrally with the hand wheel 64. Fastened to the piece 64a is a stud 66, which rotatably carries a pair of gears 67 and 68, formed out of a single piece.

. Keyed or otherwise fastened to the shaft 63 is a sleeve 69. This sleeve provides a convenient bearing for the annular piece 64a, and it also provides a gear portion 69a which meshes with the gear 67. Another sleeve 70 surrounds the shaft 63, but is not fastened thereto. This sleeve has a gear portion 70a which meshes with the gear 68.

Assuming for the moment that the sleeve 70 is stationary, it will be apparent that rotation of the elements64, 64a, and 65 will cause rotation of the screw shaft 63, but at a very much reduced speed, since the gears 67 and 68 differ slightly, and only slightly,

in diameter.

Referring now to Figs. 1 and 3, a ring 71 vers 73 and 73a, to effect theengagements, respectively,

75a, 76a. These pairs of terminals prefei' 72. The latter, as shown 1n the wlring diagram of Fig. 10, is" ,adapted to engage successively wlth rock leof contact terminals 75,76 and" ably have the construction, and mounting shown sectionally in Fig. 3 for the pair 7 5,

76. As shown in said figure, the rock'lever 73 is pivoted at 7 4;, and when the cam member 72, by engagement with said rock lever 5 drical member 78, said nuts serving to adjustably fix the initial position of the plunger 77 and also to allow of attachment of electric wires to the plunger.

tion allows a firm contact to be. made, using 5 heavy rock levers for accuracy, yet without dangerof breaking any parts.

The step-bystep rotation of the screw shaft63 to move the cross slide a on its ways 62 is induced by the reciprocatorymovement 3 of the tables 1 and 2. Referring to Figs. 1

and 5, a plate 81, attached to the front of the machine, provides a boss 82 through which extends a horizontal rod 83 suitably fastened to said boss. The rod 83 is screw 13 threaded and provides a double pair of adjustment nuts 84 and 85 which receive the thrust of a pair of compression springs 86 and. 87 respectively mounted on said rod 83. Slidably mounted on said rod 83 between 1Y5 the springs 86 and 87 is a block 88 having a hole therethrough, this block being rigidly attached to and depending from. a long bar 89. The right-hand end of the bar 89 is supported by a roller 81a located on the front of the plate 81, and the left-hand end of said bar is pivotally attachedat 90 to the depending arm 91 of a three armed lever. This lever is mounted on a stud 92 projecting from the front of the machine frame, and

provides, in addition to its depending arm 91, a pair of upwardly extending arms 93,

and 94. Arm 93 has attached thereto a hardened block. 95 providing an inclined or cam surface, while arm 94 provides a roller 96 which lies in the path of a block 97. The

block 97 is adj ustably fastened to the table 2 as by means of the usual hand screw nut 98 and screw rack 99 f0 med on said table.

In the normal reciprocatory movement of the tables 1 and 2 to cause the grinding wheels 5 and 6 to grind one or more workpieces in the" chuck 9, the block 97, at each end of the inward stroke of said tables, en-' gages the roller 96 and rocks the lever 91 in a clockwise direction. This draws the long bar 89 to the. left, against the tension of the spring 87, and causes a cam membery 100 to engage and lift a roller 101. The vroller 101 is carried by a member 102 that is pivotally mounted at 103 onthe machine frame, as

The above construcshown in dotted lines in Fig; 1. When the roller 101 and consequently also the member 102 is raised as aforesaid, a pawl 104, which is pivotally carried by said member 102, is

pressed into engagement with a cam member 105 and is thus forced towards the ratchet whee1 65 and moves it. The pawl 104 is normally kept out of engagement with the ratchet by means of a spring device not shown, and thus the cross feed mechanism can be freely turned in either direction by means of a hand wheel 64: except when the cam member 100 is actually engaging the roller 101. The'cam member 105 is adjustable to force the pawl toward the ratchet wheel either at the inception of its stroke or at any predetermined point in said stroke, and by,

this means the amount of feed can be adjusted. J a

This automatic step-by-step movement of ratchet 65in response to the actuation of pawl 104, induced by the reciprocation of the table 2 (which as heretofore clearly described moves in unison and in exact accordance with the table 1 only always in the opposite direction of travel) moves the annular member 64a, and consequently also the ring 71 and the cam projection 7 2. The front projecting portions of the rock levers 73, which as clearly shown in Fig. 3, desirably have the shape of hell crank levers, lie in the path of this cam projection 72, and consequently move-. ment of the latter causes contact between first one pair of terminals 75. 76 and subsequently betweenthe other pair of terminals. Forthe relation between the two sets of similar contact mechanisms, described in a single description above. see Fig. 1 and also the wiring diagram of Fig. 10; in the latter figure the terminals 75 and 76 that are first brought togetherin the operation of the materminals 75 and 76 are brought together, an

electric circuit is closed which, by the mechanism presently to be described, causes the tables 1 and 2 to simultaneously withdraw the respective grinding'wheels 5 and 6 a limited distance from the work, and simultaneously causes a-pair of wheel dressing devices'or diamonds 107 and 108 to move into the amplified paths of said grinding wheels, thereby to true the periphery of the latter as they pass ithe points of said diamonds.

As shown the wiring diagram of Fig. 10, electric current may be supplied by a generator 109 driven continuously by any suitable means, for example by the shaft 18. One terminal of this generator 109 is grounded as shown at 110 and the other is connected by a supply wire 111 to the lefthand bar or plate 112 of a-switch,the latter being designated as a whole by the numeral 113 and being disposed as shown in Fig. 1 on the front of the machine. Said switch 113 provides another contact plate or bar 114 arranged to the right of the bar 112 and adapted to be alternately connected and disconnected from said bar 112 by a con' other position of movable member 116 the plates or bars 112, 114 are entirely disconnectedt When the grinding wheels 5 and 6 are taking the preliminary cuts on a workpiece or workpieces, the oscillatory switch member 116 occupies said normal position of Fig. 10 and under these conditions the supply wire 111 from the generator 109 is connected to a wire 118 running from the plate or bar 114 of the switch 113. Said wire 118 runs to the coil of an electromagnet 119 disposed on the front of the machine, as shown in Fig. l. 11. return wire 120 from the coil of this electromagnet 119 connects it to the contact terminal 76. When the terminals and 7 6 are brought together as above described, by the action of the cam 72, the circuit through electromagnet 119 is completed, since the terminal 7 5 is grounded as shown at 121, Fig. 10. This energizes the electromagnet 119, causing attraction of an armature member 122, and the consequent elevation of its attached lever arm 123, these parts being pivoted at 124 on the front of the machine.

Such movement of the leverarm' 123 responsive to the engagement of cam 72 with the first rock lever 7 3 is made use of to automatically interrupt the grinding operation for the dressing and truing of the wheels 5 and 6. 3 This involves the withdrawal of the grinding wheels 5 and 6 from the wheel head 10, and the disposal, in their temporarily amplified path of movement of the dressing devices or diamonds 107 and 108 respectively; these two operations are effected through the medium of the lever arm 123 in the following manner Referring to Fig. 1, the lever arm 123 has a downward extension 125, which is slidably connected to a valve member 126. The latter is best shown in the fluid pressure diagram of Fig. 9, and as shown in said figure, the valve member is adapted .to connect piping 127 shunted into the main pressure piping 35150 diamond operating piping 128. To that end a valve casing 129 in which the valve 126 is located provides three ports 130, '131, and 132 which are, in order, a fluid entrance port 130, a fluid exit port 131 connected to the pip'- ing 128, and a. discharge port 132. When the valve member is in the position shown in Fig. 9, which it assumes prior to the energization of magnet 119, pressure fluid can not go through the valve ;--0n the contrary,the piping 128, which leads to the diamond controlling mechanism, is in direct connection with the -discharge port 132, allowing the fluid to be discharged into the main supply tank already mentioned. When however, the valve 126 is moved, as above set forth, a reduced portion 133 on said valve 126 allows the pressure fluid to enter the piping 128, and at the same time the solid portion of said valve 126 closes the exhaust port 132.

The piping 128 leads to a port 134 in a hollow cylinder 135 which is located on the back of the machine and supported by the cross slide 100. The relation of this cylinder to the machine as a whole is best illustrated in Fig. 2, whilethe fragmentary isometric View ofFig. 7 shows its relation to the rest of the diamond operating mechanisms. Referring the cylinder 135 provides a piston 136 whose rearward movement, in response to the pressure of the fluid admitted tothe cylinder 135 lowers both of the diamonds 107, 108 into the path of the grinding Wheels 5 and 6.

The diamonds 107 and 108 are embedded in metal plugs or nibs which are held by oscillatory members mounted in antifriction bearings, and delicately adjustable in their opera tive' positions by means of knobs 137 and 138 respectively. The construction and mounting of the oscillatory members which hold the diamonds, the stops which locate them at'a definite plane when moved into the paths of the grinding wheels 5 and 6 and all other details of the supports for said diamonds form no part of the present invention, beingfully described in U. S. Letters Patent Guild and Grimshaw. It is sufficient-to note for the purpose of the present invention that the two mechanisms of the type shown in the aforesaid Guild and Grimshaw patent are provided by the present machine, these being designated generally by the numerals 139 and 140 respectively. These mechanisms are symmetric, that is to say identical in construction, but having similar parts located on opposite side-s. The oscillatory members rewhich is in engagement with the front face of a short arm 143. Said arm 143 is fastened to a horizontal shaft 144 suitably mounted in bearings 145 and 146 respectively provided by the cross slide 10a or some part connected thereto, and on the ends of said shaft 144 are fastened a bell crank lever 147 and an arm 148. An upwardly extending arm 147a of the for the moment, however, to Fig. 9,,8

N 0. 1,655,903 granted on January 10, 1928, to

constitute stops to transmit the motion of the parts 147a and 148 to said links. compression springs 151 and 152 being placed on the rods between one end of the brackets and the arms in order that the downward movement of the diamonds 107 and 108 may be. cushioned.

From the foregoing description it will be apparent that rearward movement of the piston 15 136 results in counterclockwise turning of the shaft 144, Fig. 7 which moves the arms 147a and 148 rearwardly of the machine and thus draws the links 141 and 142 in the same direction to move the diamonds 107 and 108, 2 mounted on'oscillatory members, as described in the aforesaid Guild and Grimshaw patent,

into the paths of the grinding wheels and 6.

As has been stated, the other operation inaugurated by engagement of terminals 75 and 76 is the automatic amplification of the reciprocatory path of the tables 1 and 2 to carry the wheels 5 and 6 past the dress'ng devices 107 and 108. As shown in Fig. 6, the left-hand table dog 20, which limits the out 3 going movement of the tables 1- and 2, is carried by a block 153 which, instead of being secured directly with the block 154 of dog 21, is mounted so as to be capable of sliding freely longitud nally of said table. Under normal conditions, when the tables are making their usual working reciprocation to traverse the grinding wheels 5 and 6 back and forth within the workpiece or workpieces, the block 153 of dog 20 is .held in definite spaced relation to block 155' which latter, the same as the block 154 of right-hand dog 21, is a stationary block adapted to maintain its predetermined setting or adjustment longitudinally of the table 1, as given it by any suitable adjustment or holding device, as such the hand screw nuts 156,156, applied to both blocks 154 and 155 and engaging with a screw rack 157 provided by the table 1. i

The device employed to hold the sldable block 153 in spaced relation to the fixed block 155 is here shown as a latch lever 158, pivoted at 159 on block 155, and having its free end disposed by gravity in abutting relation to a shoulder 160 on block 153, thereby holding the block 153 at a predetermined distance to the right of block 155. When the latch tended beyond the usual to the table 1, as is the case member 158'islifted to free its end from the I reciprocatory working path, and the grinding wheels 5 and 6 will be carried past the dressing devices 107 and 108 which, as already described have been moved into operative position.

This amplified travel of the tables 1 and 2 involves relative sliding movement between the table 1 and the block 153, owing to the obstruction which the reversing member 22 imposes against the dog 20 to prevent the block 153 from moving with the table; finally the block 153 brings up against the block 155, whereupon the solid backing thus afforded for the block 153 enables the dog 20 to shift the member 22. This procures reversal of the tables 1 and 2, and the left-hand movement of the table 1 thus inaugurated is caused to restorethe parts automatically to normal position in the following manner As best shown in Fig. l, a member 161 pivotally mounted on the frame of the machine and pressed upwardly by a spring 162, provides beveled or inclined surfaces at each s'de thereofwhich lie in the path of similarly' beveled or inclined surfaces provided on the underside of the slidable block 153. In the normal grinding operation of the machine the inclined surfaces on the member 162 ofier no effective obstruction to the back and forth travel of the block 153, since con tact between them serves merely to compress the spring 162. When, however, the block 153 has been freed as above described, the ensuing reversal of the table finds the righthand beveled or inclined surface of member 161 in position to contact with the left-hand bevel corner of said block, and the obstruction afiorded is sufficient to overcome whatever friction there may be tending to cause the block 153 to move to the left with the table. The block 153 being thus held stationary while the table 1 and the block 155 continue to move to'the left, the latch member 158 finally resumes its normal position relative to the block 153, the end of said latch member dropping behind the shoulder 160, and the-parts are thus automatically restored to normal position at the conclusion of each single amplified "reciprocation of the tables 1 and 2.

Said single amplified reciprocation of the tables 1 and 2=-for wheel dressing purposes is inaugurated automatically when thecontacts 7 5 and 76 are brought together, as already described, the lever arm 123 being i raised at that moment in consequence of the energization of electromagnet 119. The said lever arm 123 lies, as shown in Fig. 6, in the same vertical plane as the latch lever 158, and since the contacts 75,76 always cometogether at a definite predetermined position of the tables 1 and 2, owing to the fact that the ratchet wheel 65 is actuated from the movement of saidiables by cam means described, the parts are so proportioned that the righthand end of the latch lever 158 is located at that time above the right-handend of the lever arm 123 and raising of the latter causes said lever arm to be lifted with the result already set forth.

On this amplified dressing stroke of the tables, an arm 163, Figs. 1 and 6,'pivoted at 159 and hanging by gravity as shown, strikes an arm 164 of movable switch member 116 thereby rocking the connector 115 of said switch member away from bar 114; (see Fig. 10), which prevents a repetition of the dressing stroke.

To prevent further dressing of the grind ing wheels 5 and 6 by the dressing devices 107 and 108, when the tables 1 and 2, as will presently be described, are moved outwardly for the final separation between grinding wheels and workpieces which occurs uponcompletion of the grinding operation, the cylinder 135 must be relieved of fluid pressure, and said dressing devices moved into their inoperative positions as shown in Figs. 1 and 2. To that end automatic means is provided for returning the valve member 126 to its former position as shown in the fluid pressure dia gram of Fig. 9, in which position the pres sure fluid is cut ofl' from said cylinder 135 and said cylinder is directly connected with the pressure fluid supply tank or pump through the exhaust port 132. To that end the lever arm 123 provides a vertical surface 165 which, upon reversal of the tables 1 and 2 at the end of the aforesaid amplified dressing stroke, is engaged by a vertical surface 166 provided by a portion of the block 153. Engagement of said surfaces, since the block 153 is then moving to the right, moves the lever arm 123 in a clockwise direction, and consequently shifts the valve member 126 to the left as will be seen from a consideration of Fig. 1. p

The foregoing means relieves the diamond operating cylinder 135 and the piston 136 therein of any pressure, but it does not move the diamonds 107 and 108 to their inoperative position. Mechanical means positive in its nature is provided to agcomplish this, and it comes into operation substantially as the grinding wheels 5 and 6 re-enter, the workpiece held in the chuck 9. As shown in Figs. 2 and 7, the table 1 carries on the rear thereof a cam bar 167, which has a horizontal surface 168 andv an inclined surface 169 on its lower side. A roller 170 on the end of an arm 171 that is fastened to a shaft 172 lies in the pa'tlrof these surfaces. The shaft 172, as shown in Fig. 2, is supported in bearings 173' and 174 provided by the machine frame, and adjacent the bearing 17 1, a short arm 175 is fastened to said shaft 172. The arm 175 extends substantially horizontally and rearwardly from the shaft 172 and is connected by means of a link 176 to the rearwardly extending arm of the bell crank lever 147. It

will at once be apparent that when the inclined 142 forwardly, and thus positively raises both of the diamonds 178 as will be seen from an inspection of the aforesaid patent to Guild & (irimshaw. Engagement of the inclined surface 169 with the roller 170 occurs when the tables 1 and 2 have almost carried the grinding wheels 5 and 6 back into the workpieces being ground, and in the subsequent operation of the machine, during the recipro- In order to cause the tables 1 and 2 to travel.

at reduced speed during the dressingoperation thus to prevent the formation of grooves in the grinding wheels 5 and 6, and in order also, when desired, to cause the said wheels to take the finishing cuts on the workpiece or workpieces at a reduced traversing speed, there is provided a valve 177 ;see especially Figs. 2, 7 and 9. The construction of this valve is not illustrated herein since it may be of any desired type; it is sufhcient to note that turning of a valve shaft 178 will result in restricting the flow of fluid pressure through the valve which, as will be seen from an inspection of Fig. 9, is located in the supply pipe 35 that carries the fluid pressure to the reversing valve 23.

Referringagain to Figs. 2 and 7., the valve shaft 17.8 has suitably fastened thereto a short arm 17 9. To the end of this arm 179 is pivotally attached an upwardly extending link 180 the upper end of which is pivotally fastened to a substantially horizontal arm 1 81. The other end of said arm 181 provides a hub portion 182 mounted on a stud 183 projecting from the machine frame. The link 180 provides an outwardly extending boss 184 having a vertical hole therethrough, and a rod 185 which depends from and is pivotally attached at 186 to the arm 171 passes through said hole. The rod 185 is screw threaded, and two pairs of adjustable nuts 187 and 188 are located-thereon, the former pair being placed above the boss 184,. and the latter below it. Assuming the valve 177 to be wide open which is its position when the link 180 is depressed, admittance of fluid under pressure to the cylinder 135. withconsequent rocking-of the shaft 14:4, results in rocking of the shaft 172 cordance with the amount of turning of said shaft, and thus causes the grinding wheels 5 and 6 to move slowly past the dressing diamonds 107 and 108. .When, upon reversals of the said tables at the end of their outward amplified strokes, the said tables travel inwardly again, the cam bar 167 depresses the roller 170, as already described, and this action moves the rod 185 downwardly, repositioning the link 180 and consequently the shaft 178 more or less in accordance with the setting of the nuts 187. When, upon the completion of the grinding operation upon the particular workpiece or workpieces being operated upon, the tables 1 and 2 move outwardly for final separation between said wheels and the workpieces, a roller 189, attached to the rear of the table 1 and lying in the path of a cam surface 190 provided on the upper part of the arm 181, strikes said cam surface and moves the arm 181' and consequently; the link 180 downwardly to open the valve 17 7 to allow the maximum flow of pressure fluid therethrough; provided the nuts 187 were set so that the valve was not fully open subsequent to the dressing operation. If the valve had been reset completely, as it would be if the nuts 187 were screwed downwardly to remove all play between the boss 184 and the nuts 187 and 188,-the roller 189 will merely pass over the cam surface 190 without effect, but at all events, the machine provides automatic means for insuring that the valve 177 will be fully open at v the end of each grinding operation.

After the wheel dressing operation above described, and with theresumption of grinding, the further feeding of the work head 10 in relation to the grinding wheels 5 and 6 involves further clockwise rotation of the ring 71, which ultimately carries the cam 72 into engagement with the second rock lever which is designated 73/; on the wiring diagram of Fig. 10 to distinguish it from the first rock lever designated 73 on said diagram. The parts are so set that this engagement and the consequent rocklng of this lever 730. that carries the contact 7 5a, brings together the terminals 75a 'and 76a just as the workpiece or workpieces reach the exact desired size. This engagement of these terminals completes an electric circuit through a second electromagnet which is designated by the numeral 191 on Fig. 10 and which is located on the front of the machine, directly behind the electro-magnet 119. The electric current proceeds from the generator 109 by way of a branch 111a of the conductor-111 to said electromagnet 191, thence by a conductor 192 to the contact terminal 76a, thence through the terminal 75a into the lever 7 3a, which is grounded by reason of being uninsulated'from the machine as diagrammatically illustrated at 121 in said Fig. 10; and since, as aforesaid, the other terminal of the generator 109 is also grounded the circuit is complete. Energization of this electromagnet 191 causes attraction of an armature member 193 which, together with an inclined lever arm 194 and a depending arm 195, all convenieiitly formed in one piece, is pivotally mounted on the same spindle 124 which'forms the pivot for the armature member 122 and its similar associated parts.

The depending arm 195 is connected to a slidable valve 196 located in a valve casing 197, said valve and said casing being located directly behind the valve member 126 and the casing 129 respectively. Refer to Fig.1 for the position of these parts and to Figs. 9 and 10 for the construction. As is the case with the casing 129, the valve casing 197 provides three ports 198,199, and 200, which are respectively a-fluid entrance port, a fluid exit port, and a discharge port. When the valve member 196 is moved tothe right by energization of the electromagnet 191, this slidable valve mechanism, which may be idenpressure diagram of Fig.- 9. and the fragmentary view of Fig. 4, and movement of this piston in response to fluid pressure actuation causes the grinding wheels and the workpieces to be immediately separated in a direction laterally of the machine in the following manner.

As shown in Fig. 3, the screw shaft 63 is provided with a shoulder 204 and spaced from this shoulder 204 is the right-hand threaded end of the shaft, which is adapted to receive a nut 205. Between the shoulder 204 and said threaded end, the shaft 63 is a plain cylinder, and on this cylindrical portion are the inner races of a pair of ball bearings 206 and 207. The inner race of bearing 206 bears against the shoulder 204, while the inner race of bearing 207 is engaged by the nut 205-,- The outer race of bearing 206 engages a shoulder 208, while the outer race of bearing 207 engages a shoulder 208a, both of said shoulders being provided on the internal cylindrical surface of a member 209.

The member 209 is externally threaded and is received in a threaded portionof a member 210 which, as shown in Fig. 4, is fastened to the machine frame below the ways 62. lit will be seen that so long as the member 209 remains unmoved, the shaft 63 will be held from axial movement, and consequently the position of the cross slide a upon the ways 62 will depend upon the rotation of said screw shaft responsive to the automaticfeed as already described, but that turning of the member 209 will shift the whole screw shaft 63 and for that matter also the hand- Wheel 64 and associated parts on the front of the machine in a lateral direction. The member 209 is adapted to be turned upon movement of the piston 203, and to that end an arm 211 which provides a collar portion 212 suitably fastened to the member 209 is engaged by the end of the piston 203 as clearly shown in Fig. 4. Admission of fluid pressure to the cylinder 202, therefore, which occurs almost instantaneously with the energization of the electromagnet 191 causes the member 209 to be turned, thus moving the screw shaft 63 rectilinearly, and the direction of the threads on the member 209 and 210 are such that this shifting of the screw shaft 63 moves the work head 10 towards the back of the machine, thus moving the ground workpieces laterally with respect to the grinding wheels 5 and 6 and definitely termi nating the grinding operation. This lateral separation of the grinding wheels and work piece or workpieces prevents scratching or marring of the highly polished finished surfaces as the grinding wheels emerge therefrom.

Energization of the electromagnet 191 effects such emergence, causing the tables 1 and 2 to travel outwardly of the machine away from each other and thus carrying the grinding-wheels 5 and 6 away from the work head 10, so that the operator can remove the finished workpiece or workpieces from the chuck 9. To that end the left-hand table dog is pivotally attached to its carrying block 153 and normally rests by gravity in the position shown in Figs. 1 and 6, thereby maintaining its free-end in position to engage and move the reversing member 22 at the end of the outgoing normally working stroke of tables 1 and 2. -When the magnet 191 is energized the lever arm 194 is raised into the path of dog 20 and the latter, on the aforesaid outward movement of the tables, by reason of its pivotal mounting, is free to ride on the upper surface of said lever arm; thus the striking end of said dog 20 is carried clear of the reversing member 22 and the tables continue their outward movement, carrying the grinding wheels hand 6 away from the work head 10 and past the then inoperative dressing devices 107. and 108.

Such final motion of separation between the grinding wheels 5 and 6 and the work head 10 at thefinish of a given grinding operation returns the speed control valve 177 to its normal wide open position by the action of roller 189 on the cam surface 190, as has been described. The motion of separation likewise resets the externally threaded memher 209 to its initial position, thus shifting the screw shaft 63, so that in a subsequent grinding operation the dressing operation and the cessation of grinding will be brought about at the proper stages in said grinding operation, as determined by the position of the cross feeding elements modified by the action of the cross feed compensating mechanism. The latter mechanism is also operated by the final movement of separation and compensates the feeding mechanism for wear of the grinding wheels and for the material taken therefrom by the dressing operations. Finally the tables are brought to a stop in the retracted position by any suitable mechanism, such as that disclosed in the aforesaid patent to Heald and Guild No. 1,582,468 and thus the given grinding operation is completed and the operator may stop the rotation of the chuck 9, remove the finished work and insert a new piece or pieces.

Such automatic stopping mechanism may take the form of a poppet valve 214 whose head is located in a chamber 215 of the passage 32 an d which is normally kept open by a cam member 216 carried by the table 1 and engag ng a lever arm 217 which holds said valve 2 .4 open against the tension of a spring 218. When the tables are running outwardly the pressure fluid is returning through the passage 32 past'the poppet valve 214, and when the tables reach a certain position the cam m mber 216 releases the lever arm 217, thus allowing the poppet valve 214 to close under the simultaneous action of the spring 218 and the flow of fluid and this, of course, as it locks the fluid in the cylinders and 26, stops the movement of the tables. It will be apparent that the closure of this valve 214 is no obstacle to restarting of the tables in the opposite direction, as the force of the flu d flowing outwardly through the passage 32 will open it.

The work head 10 is reset automatically to the position it occupied at the completion of the grinding operation just as soon as the grinding wheels 5 and 6 have fairly emerged from the workpieces, and this takes place through positive returning of the lever arm 194 and consequentlyalso of the valve 196 to their original positions, thus cutting off the fluid pressure from the cylinder 202, and opening said cylinder to the exhaust through the port 200. This repositioning of the lever arm 194 is brought about by contact with said arm of the lower corner 219 of the table block 155 as the table 1 travels to the right. There being then no pressure against the piston 203, the latter is returned to its initial position inside the cylinder 202, as shown in Fig. 4, by means of a strong spring 220 acting on the depending arm 211, and this, of course, turns the member 209 in a counterclockwise direction, Fig. 4, and moves the screw shaft 63 laterally into its normal position.

Referring now to Figs. 1 and 5, the table 2 has attached thereto a pivot stud 221 which carries a short arm 222 hanging downwardly therefrom by gravity. The arm isfree to turn clockwise to a horizontal position, there being nothing to stop it from moving in this direction, but it can not be moved counterclockwise beyond the vertical position in which it is shown in the drawings, because a shoulder 223 provided by the table or a member 224 fastened to the table and into which the stud 221 is conveniently screwed, backs up said arm 222 and causes it to be rigid and unyielding when forces are applied to move it counterclockwise. In the final movement of separation of the tables 1 and 2 as already described, the arm 222 strikes the inclined surface of the hardened plate 95 on the arm 93 the three arm member, and. thus depresses the arm 93, swinging the member as a ole in a counterclockwise direction, and this action moves the long bar 89 to the right. At the right-hand end of the long bar 8 9is a block 225 which normally is barely in contact with a roller 226 provided by a bell crank lever 227 pivoted at 228 on the front of the machine. Movement of the long bar 89 to the right consequently turns the bell crank lever 227 in a clockwise direction and draws a link 229 attached to one end of said bell crank lever downwardly. The link 229 is connected at its other end to an arm 230 which is fastened to a shaft 231, and the consequent downward movement of the link 229 procures lim' ited clockwise rotation of the shaft 231.

Suitably fastened to the front end of the shaft 231 is a member 232. Said member, of course, receives the clockwise rotation referred to, a spring 233 together with the spring 86 returning the parts to normal position immediately after the operative engagement of the arm 222 and-the plate 95. The member 232 pivotally carries at 234 a pawl 235. The latter contains a spring pressed plunger device urging it upwardly, but a pin 236 holds the pawl 235 in the position shown, until the member 232 is moved inwardly. lVhen this occurs, the pawl 235 engages and moves a ratchet wheel 237 which is keyed or otherwise fastened to the sleeve 70. This action moves the ratchet wheel and consequently the sleeve 7 O'fland gear 7 8 through an angular distance that is adjustable in a manner which need not be herein specified, and consequently changes the relation between the annular-member 64a which carries the cam 72 and the cross feed screw shaft 63, and therefore compensates the machine for wear of the grinding wheels 5 and 6, by causing the dressing operation to occur at aslightly dilferent position of the work head 10 and cross slide 10a for each successive grinding operation. This insures contact between the wheels 5 and 6 and the dressing diamonds 107 and 108, the invariable subsequent advance of the cross feed being relied on to bring the workpiece to a definite size, since the dressing diamonds, during the dressing rotation of the chuck 9 to remove the ground workpiece or workpieces and insert unground ones in the said chuck as soon as the tables 1 and 2 have come to a stop, there is provided a lever 240 on the front of the machine, which controls a clutch and brake mechanism. See Fig. 1. As shown in Fig. 2, a shaft 241, which is connected to the shaft 242:0f the lever 240 {in any suitable manner, provides a depending arm 243, which is connected to a long link 244 that is in turn connected to a bell crank lever 245. The latter is adapted to actuate a toggle link connection 246 extendingfrom a lever 247 that is pivoted at 248 to the machine frame. Mounted on the same pivot 248 is a brake lever 249, the brake shoe of which is applied to a drum 250 when the operator has moved the lever 240, the parts being shown with the brake applied in Fig. 2. The connection between the lever 247 and the brake lever 249 is through the medium of a long stud 251 which is provided with a compression spring 252; the bottom of the lever 247 is likewise connected by means well known in this art to one element 253 of a cone clutch. As the pulley 17 is formed integrally with the brake drum 250, it will thus be seen that the operator can quickly control the r0r tation of the pulley from the front of the machine, and thus start and stop the chuck 9 at will. i

The machine parts being in the position illustrated in Fig. 1 as the result of a previous grinding operation, the operator, after having inserted an unground workpiece or workpieces in the chuck 9, starts the machine in operation again by the shifting of a control lever 254 on the front of the machine. This operates thevalve member 23 to cause the tables 1 and 2 to move towards each other and towards the wheel head 10; the table revcrsing'dog 20, when it strikes the reversing member 22, is lifted thereover by reason of its pivotal mounting. During the inward travel of the tables to the grinding position, an arm depending from the block 155 and extending in the opposite. direction to the arm Air;

'mechanism being actuated at the end of each inward stroke of said grinding wheels. There is no assurance that the actual contact between the wheel and the surface it is to grind will occur simultaneously with contact between the wheel 6 and the surface that this "wheel is to grind; on the contrary if the amount of stock to be reduced from the different surfaces is different, the initial con tact will take place at difierent times. In practice, the operator may and usually will turn the hand wheel 64 until contact is made on one side or the other, thus speeding the operation of the machine. When, however, actual grinding is taking place at both sides of the work head, both surfaces that are being ground bear the same relationship to their ultimate finished diameters. The machine of thepresent invention thus makes use of the principle that if a plurality of variables, while approaching their respective limits are always equal, their limits will be equal.

The foregoing relationship between the wheels and workpieces is exactly true only on the assumption that the grinding wheels wear at the same rate. This assumption, however, as hereinbefore pointed out, cannot be relied upon, and therefore the machine provides the automatic dressing instrumentalities hereinbefore described to overcome non-,

uniformity in wheel wear, and to re-synchronize the relationship between the grinding wheels as close to the time when the grinding operation will cease as is possiblev The grinding, therefore, proceeds until such time as the first electric circuit is closed by the coming together of the contacts and 76, whereupon both tables withdraw outwardly and the grinding wheels are dressed and trued as already described. lln this outward movement of the tables, the depending arm 163 strikes the arm 16% of the switch member 116 and thus makes the machine ready for the final withdrawal stroke of the tables, but it should be noticed that the movement of the table 1 is notsufficient in this dressing stroke to carry the arm 255 past the switch arm 256- The grinding is now resumed and the cutting surface of one wheel is exactly the same distance from the desired size of the work surface that it is grinding as the cutting surface of the other wheel is to the finished size of the work surface that it is operating upon. Uwing to the smallness of the crossfeed movement required of the workhead 10 between the dressing operation and the completion of the grinding, this equality of the variable remains substantially undestroyed, and ,both surfaces are completed at the same moment as signified by the bringing together of the contacts 750: and 7 6a, which immediately causes both tables to withdraw to theinoperative position shown in Figs. 1 and 2.

The machine is not limited to the grinding of holes of the same size, for a small grinding wheel 5 might be employed on one side of the machine and a large grinding wheel 6 on the other side to grind a larger diameter hole, and the difierence in the amount, by weight, of the material removed would be compensated for by the greater peripheral speed of the larger wheel, and the machine will thus efiectively operate with the same rate of lateral feed for different sized workpieces. Obviously the grinding wheels 5 and 6 do not have to be in axial alinement on their respective tables 1 and 2, and the invention contemplates the adjustability of the work heads 3 and 4 transverse to the line of reciprocation of said tables, but the setting of the machine is somewhat facilitated by having the grinding wheels located in alineinent.

The invention possesses great utility in grinding cluster gear pieces, or in the grinding of pulleys or clutches or similar articles that have several surfaces to be ground of equal or different diameters. The machine as shown can even grind as many as four distinct surfaces not located in any given geometrical cylinder, merely by providing two grinding wheels of different diameters on each spindle 7 and 8 and duplicating the dressing points 107 and 108 on each side of the machine. For these and many other purposes for which the machine can be used, it presents very great commercial utility and advantage, as the automatic grinding of a plurality of surfaces by the same operation and setting of the machine accomplishes a tremendous saving.

I claim,

1. In the art of grinding, the improvement which consists in causing a plurality of grinding elements initially bearing a variable relation to a plurality of surfaces to be ground,

to bear always equal relationships to said surfaces, by relative advance of said surfaces in respect to said elements, and periodic dress- 1ng of said elements to known positlons and thereafter to synchronously advance to known limits, thus to cause their limits, which meas ure the finished size of the several work surfaces, to be equal,

2. lln a grinding machine, the combination with a. pair of grinding wheels and means to rotate them, of a pair of tables or carriages upon which said grinding wheels are mount-.. ed, means to reciprocate said carriages, and separate means to synchronize their reciprocations that their simultaneous strokes occur always in opposite directions.

3. In a grinding machine, the combination with a pair of tables or carriages adapted to produce relative traversing movements between grinding wheels and workpieces, of fluid pressure operated means to actuate said carriages independently, and mechanical means connecting said tables to cause them to move synchronously and always in opposite direct-ions,

4:. In a grinding machine, the combination with a pair of tables or carriages adapted to produce relative traversing movements between grinding wheels and workpieces, of fluid pressure means to actuate said tables independently, valve means having connections for controlling the adinission of fluid to said fluid pressure means so arranged that the tables will always move in opposite directions, and means to operate said valve means from a given table. a

5. In a grinding machine, the combination with a pair of tables or carriages adapted to produce relative traversing movements between grinding wheels and workpieces, of fluid pressure means for reciprocating said tables independently, connections for admittingpressure fluid to and discharging it from said means, to operate said tables, a single valve means controlling flow of fluid through said connections, and a single operating means actuated by one of said tables to shift said valve -means, whereby said tables will operate synchronously.

6. In a grinding machine, the combination with a pair of tables or carriages adapted to produce relative traversing movements between grinding wheels and workpieces, of fluid pressure operated means operating said tables, connections for admitting and discharging fluid from the operating means to operate said tables, a single valve means controlling flow of fluid through said connections, a single operating means actuated by one of said tables to shift said valve means, and mechanical means connecting said tables to force them to move in unison despite variations in the amount of pressure exerted upon each or the amount of resistance said tables encounter.

7. A grinding machine having in combina tion, a rotary work holder, a pair of grinding elements, meansto reciprocate said grinding elements in unison to cause them to operate on work in said work holder, and means automatically operable at a redetermined time before the completion of the grinding operation or operations to prolong one stroke of each of said elements in different directions to eifecta temporary separation between said work holder and said elements.

8. In a grinding machine, a pair of grinding wheels, means for effecting a working traverse between each wheel and the work by means of separate tables or carriages, means operable automatically before the completion of the grinding operation to amplify the movement of each of said tables, a pair of dressing devices applicable to dress the said wheels at this stage, and means for causing both of said tables to automatically resume" their working traverse after said dressings for the final and finishing cuts of the grinding wheels to bring said work to size.

9. In a grinding-machine, a pair of grinding wheels having separate and oppositely moving traverses in relation to the work, means for automatically amplifying said traverses in opposite directions when the work, by grinding, has reached a predetermined size, means i'or automatically disposing a wheel dressing device in the path of eachwheel on said amplified traverse thereof, and means forautomatically resuming the normal reciprocatory working traverses between grinding wheels and work to bring the lat ter to the desired finished size. I

10. In a grinding machine, a pair of grinding wheels, means for effecting a working traverse between each wheel and the work by means of separate tables or carriages, means operable automaticallybcfore the completion of the grinding operation to amplify the movement of each of said tables, a pair of dressing devices applicable to dress the said wheels at this stage, and means for causing both of said tables to automatically 'resume their working traverses after said dress: ings for the final and finishing cuts' of the grinding Wheels to bring said work to size and means to compensate for attrition of the wheels due to wear and dressing.

11. In a grinding machine, a pair of grinding wheels having separate and 0ppositely moving traverses in relation to the work, means for automatically amplifying said traverses in opposite directions when the work, by grinding, has reached a predetermined size, means for automatically disposeach wheel on said amplified traverse there- 1 of, means for automatically resuming the normal reciprocatory working traverses between grinding wheels and work to bring the latter to the desired finished size, and means operable by one of said tables for effecting relative compensation between said wheels and the work, for the attrition of said. wheels, due to wear and dressing.

mg a wheel dressing device in the path of 12. In a grinding machine, the combination with {a pair of tables or carriages adapted to produce relative traversing movements between grinding Wheels and workpieces, of fluid pressure operatedmeans to actuate said carriages independently, of means to cause the carriages to make an extended stroke upon the completion of the workpieces, and mechanical means connecting said tables to cause them to move synthey will bear a variable relation to a plurality of finished surface loci as the cross teed operates, but an always equal relation thereto, the limit of advance measuring the finished loci of the workpieces.

1a. In a grinding machine, a rotatable yvorkholding means for a plurality of Workpieces, a pair of grinding elements, one on either side of said Workholding means, means to reciprocate said grinding elements relative to said workholding means, whereby each grinding element will traverse a Workpiece, means to synchronize the traversing motions of said elements, means to impart a relative cross feed between said elements and said Workholding means to cause the said elements to cut deeper and deeper into the respective workpieces, a pair of dressing devices, means governed by the progress of the grinding operation to cause the said grinding elements to withdraw from the workpieces and be dressed simultaneously by said dressing devices, means to return said elements to the workpieces, for further grinding after said dressings, and means governed by the further progress of the grinding operation to cause a combined relative lateral and longitudinal separation of the grinding elements and the workholding means, to permit removal of said ground workpieces from the said workholding means.

WALDO J. amen. 

